Gyroscope



Aug. 8, 1950 L. HAMMOND 2,517,786

GYRoscoPEs Filed oct. 2s, 1942 4 sheets-sheet 1 a are/2S Ham/22 ond Aug- 8, l950 HAMMOND 2,517,786

GYROSCOPES Filed Oct. 28, 1942 4 Sheetsheet 2 ff? Vera for .la are/25' fa/72m of? a L. HAMMOND Ailg. s, 195o GYROSCOPES 4 Sheets-sheet 5 Filed Oct. 28, 1942 Aug- 8, l950 L. HAMMOND 2,517,786

GYROSCOPES Filed Oct. 28, 1942 4 Sheets-Sheet 4 PEBMHNENT FIELD Patented Aug. 8, 19.50

GYROSCOPE Laurens Hammond, Chicago, Ill., assignor to i Hammond Instrument Company, Chicago, Ill., a corporation of Delaware Application October 28, 1942, Serial No. 463,643

(Cl. M -5.47)

'7 Claims.

My invention relates generally to gyroscopes and more particularly to improvements in gyroscopic mechanisms suitable for use in gyro-pilot systems.

It is an object of my invention to provide a gyroscopic mechanism incorporating improved erecting means.

A further object is to provide an improved gyroscopic mechanism which is electrically operated and controlled, and in which the directional gimbal is relatively insensitive to externally applied torques, while at the same time has its position in space very accurately controlled by the gyro.

A further object is to provide an improved electrical gyro erecting apparatus.

A further object is to provide an improved gyroscope which is relatively insensitive to temperature changes and will maintain its accuracy when used at the low temperatures prevalent at high altitudes.

A further object is to provide an improved directional gyroscope which is extremely simple and rugged in construction, and which may be economically manufactured.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Figure 1 is a side elevational View of the gyroscopic mechanism;

Figure 2 is a plan view thereof;

Figure 3 is a fragmentary sectional View taken on the line 3-3 of Fig. 1;

Figure 4 is a fragmentary sectional view showing the insulated pivot bearing for the gyro casing;

Figure 5 is a fragmentary side elevational View of the gyro casing taken generally on the line 5--5 of Fig. 3;

Figure 6 is a longitudinal sectional view taken on the line 6 6 of Fig. 3;

Figure 7 is a fragmentary sectional view taken on the line 'l-T of Fig. 3, being shown to an enlarged scale;

Figure 8 is a fragmentary sectional view takenl:

on the line 8-8 of Fig. '7;

Figure 9 is a sectional detail showing the mounting of the slip rings;

Figure 10 is a horizontal sectional view taken on the line l-lll of Fig. 1;

Figure 11 is a fragmentary sectional View taken on the line H-Il of Fig. 3;

Figure 12 is a fragmentary end elevational view showing the gyro uncaging mechanism and taken on the line I 2-12 of Fig. 1;

r shaft 32 by screws 31, 39.

Figure 13 is a fragmentary sectional view taken on the line l3--l3 of Fig. 12;

Figure 14 is an electrical wiring diagram of the apparatus;

Figure 15 is a fragmentary horizontal sectional View showing a modified form of the erection controlling switch mechanism;

Figure 16 is a fragmentary side elevational View of the switch mechanism of Fig. 15;

Figure 17 is a sectional View taken on the line I1-I1 of Fig. 16; and

Figure 18 is a wiring diagram of the electrical apparatus in which the modified form of the erection controlling switch is employed.

Referring to Figs. 1, 2 and 3, the gyroscopic apparatus is illustrated as mounted in a suitable frame comprising a flanged base 20, a flanged top 22, suitable flanged end wall 24, and partial side Walls 26, these portions of the frame being preferably welded together to form a strong rigid structure.

The gyro rotor (Fig. 6) is secured to an armature shaft 32 of an electric motor 34 by a fastening plate 36 attached to the rotor 30 and The shaft 32 is mounted in anti-friction bearings 38, 4|! illustrated as ball bearings, the shaft being secured to the inner race of the ball bearing assembly 38, such fact being indicated in Fig. 6 by striations on the shaft. The shaft is, however, free to move longitudinally relative to the ball bearing assembly 40, such fact being indicated by exaggerated clearance between the shaft and bearing 40. The outer races of ball bearings 38 and 4l) are iixedly secured in the motor housing 42, and the position of the shaft 32 with respect to the motor housing 42 is maintained by a pair of spring washers 44 and a flat washer 46 which are slightly compressed longitudinally of the shaft 42 so as continuously to exert a force be tween the inner race of ball bearing assembly and the shaft 32, one of the washers bearing against the end of the commutator 48 but of course being suitably insulated from the segments thereof.

The bearing 38 is located substantially at the center of gravity of the gyro and parts spinning therewith. When the assembly is subjected to temperature changes, the resulting thermal expansion of the parts will therefore not cause a material shift in the center of gravity of the spinning gyro parts. This is because the longitudinal position of the shaft 32 and parts carried thereby is determined solely by the ball hearing 38 the shaft being continuously pressed to the right (Fig. 6) by thev spring washers 44 s as to take up any clearance in the bearing 38. The rotating parts are thus located at the center of gravity, thermal expansion will be outward from the center of gravity in both directions, and thus will have a minimum eect upon the location of the center of gravity.

A hanged frame 50 is rigidly secured to the motor housing 42 by a plurality of screws 52 which are threaded in studs 54, the studs being staked to the motor housing 42. The screws 52 also secure a rotor housing part 56 to the frame 50 and motor housing 42. The housing for the gyro rotor 30 is completed by a anged cap 58 which is pressed over the housing part 56. The gyro rotor housing formed by the part 56 and cap 58 is preferably not airtight, such fact being indicated by a vent opening 60 formed in the cap 58. A pair of studs 62, 63 are riveted to the flanges of the frame 58 and extend vertically to provide supports for adjustable balancing weights 64 which may be held inadjustedposition by lock nuts 66. The screws 62 and 63 are located in a vertical plane passing through the axis of the gyro shaft 32, and thus are utilized to balance the gyro assembly with respect to this plane.

Studs 68, 69 are riveted in the frame 50 and lie in a horizontal planepassing through the axis of the shaft 32, these studs being provided with adjustable weights threaded on the studs and held in adjusted position by lock nuts 12. 'If desired, one of each of the pair of the adjusting Y studs 62, 63 and 68,'- 68 may beomitted, since accurate balance of the gyro casing assembly may readily be obtained by the use of only one of each of these pairs of studs.

The gyro casing assembly is mounted for pivotal movement in a vertical gimbal 14. The terms vertical and horizontal are used herein merely in their relative sense, since the apparatusmay of course be mounted in any desiredposition. Pivotal mounting for the gyro casing' assembly comprises an insulating bearing '(Fig. 4) composed of a bolt 16 secured to the vertical gimbal 14 and insulated therefrom by suitable washers 18, the bolt being bored to provide a bearing for pivot pin 80 projecting from a boltV 82 which is secured to the ange of frame 50, being suitably insulated therefrom by washers 84.

Soldering lug washers 86 and 88 are in electrical connection with the bolts 16 andY 82 respectively. The contact of the'pivot pin 80 with the bearing formed by bolt 16 thus provides an electrical connection between the soldering lugs 86 and 88. The soldering lug 88 is connected by a conductor 80 to the motor 34, the other'terminal of the motor being grounded to the frame 50 by a conductor 88. The frame '50 is grounded-to the vertical gimbal 14 through its other horizontal bearing which comprises a stud 8| threaded in the vertical gimbal 14 and locked bywa nut 82. The stud 8| provides a bearing for a pivot pin 94'projecting from a stud 86 which is secured' to the flange of frame 50 by a nut 98. rPivotal movement of the gyro casing assembly'with respect to the vertical gimbal 14 is limited by the engagement of a stop pin |00 (Fig. 5) with the edge of the gimbal 14, the pin |00 being riveted to an arm 5| extending' from thek frame 50. 'The stop pin |00 thus limits pivotal movement of the gyro casing with respect to the gimbal 14 to an angle of approximately 120.

Pivotal movement of the gyro casing with respect to the gimbal` 14 causes operation of an erection controlling switch |02 formed by a pin bearing member tween the washer |38l and gear |40.

|04 projecting from the stud 96, and preferably having a contact wire |06 welded thereto. The other contact of the switch |02 is provided by a contact wire |08 welded to the end of a flexible switch arm M0. This switch arm ||0 is riveted to a bracket ||2 which is secured to the vertical gimbal 14, but insulated therefrom. The support for the bracket ||2 comprises an arm ||4 riveted to the gimbal 14 and a bolt ||6 which is suitably insulated from the arm ||4 by insulating washers I8. The bracket |2 is provided with a stop portion |20 which limits the extent of ilexure of the switch arm H0.

The gimbal 14 is mounted for pivotal movement about its vertical axis, this mounting comprising `a bearing pin |22 which is secured in a bushing |24 staked in the bottom wall of a gear housing |26, the latter being suitably secured to the base 20. A bearing member |28 is drilled to receive Vthe bearing pin |22 and is rigidly secured to lthe gimbal 14 by a nut |30. A ball bearing |32 prov vides af thrust bearing `for supporting the gimbal 14, this ball bearing |32 being locatediibetween the upper endof the hardened pin |22 and fthe "inner end of the drilled holeY |34 formed inthe bearing member |28.

yA washer' |36 is staked to the lower end ofthe |28 and supports a friction washer |38 which may be made of any suitable material such as a phenol condensationproduct. A gear |40 rests upon theV friction washer |38, be-

'ing held in contact therewith by a compression coil spring |42, the upper end of which abuts against a thin steel washer |44 resting `against a suitable shoulder on the'bearing member |28.

'The frictional engagement of the gear |40 with the friction'washer |38 providesa yieldingdriving connection'between the gear 40 and the gimbai 14, the amount of` this friction being vdetermined by the compression of the spring |42,'while the spring |42 also acts partly as'a torsion spring,

` resisting relative movement between the gear |40 and the member |28, although. the latter eiect'of the spring is small compared with the frictionbe- The .gear |48 is driven by a reversing motor |46 which is suitably mounted onA the side frame panel 26 and base 20 and has an armature shaft |48 projecting through the base 20 andcarrying a pinion |50. The pinion |50 is Vgeared to thegear |40 through a train of speed reducing gears and pinions (Fig. l0) mounted on shafts |52 whichare provided with suitable' bearings Ain the Vbase 20 and gear housing |26.

The upper bearing for the gimbal 14 is provided by a bearing bushing |60 (Fig. 9)whi'ch is'staked in the flanged top 22 of the main frame. "A shaft |62 is pressed in a bushing |64 so as to 'be rigid therewith, and this bushing is'staked in the 'gimbal 14, the bushing |60 and shaft |62 .thusforming the upper pivot for'theY gimbal `14.

The bushing |64 forms aV support for a pair of slip rings |66, |61 which are rigidly secured to the bushing but insulated therefrom by a sleeve |68 and washers |69. 'The Vslip rings |66, |61 are provided with grooved anges "|10 which are formed to receive contact'brush ywires |12 (Fig. 11) which are welded to the ends of brush arms |14 and |16. These brush arms are pivotally mounted on terminal bolts V|15 and |11 respectively, being secured to but insulated from the top 22 of the main frame (Fig. 3). A wire |18 connects the soldering lug 86 with a lug |80 (Fig. 9) which is formed fromv the slip ring |61 and projects through a suitable opening formed in the slip ring |66, the opening being provided with an insulating grommet |82. The brush arms |14 and |16 have their contacts |12 resiliently held in the grooves formed in the flanges |10 of the slip rings |66, |61 by a pair of tension springs f |84, |86 (Fig. 11) which are anchored to an insulating block |90, the block |90 being suitably secured to the frame top 22. The slip ring |66 is connected by a conductor |92 with the switch arm of switch |02.

Means are provided to lock the gyro in caged position, such means being best illustrated in Figs. 12 and 13, and comprising a leaf spring |94 secured to the end wall 24 and having a pin |96 riveted thereto. The pin |96 is adapted to project through a suitable opening |98 in the end wall 24 and into a socket 290 formed in the motor housing 42. When the gyro is caged the pin |96 engages in the socket 200 and is held in engagement by a lever 202 which is pivoted on a stud 204 and has an end portion 225 which is adapted to overlie the end of the leaf spring |94. rThe lever 292 is urged into gyro uncaging position by a tension spring 298, oneend of which is anchored to the end wall 24, and the other end of which is secured to one arm of a bell crank lever 2|0 which is suitably pivoted to the end of the lever 202. The other arm of the bell crank lever 2|0 has a release cord `2|2 secured thereto.

Pivotal movement of the lever 202 is limited by a pair of stop pins 2|4, 2|5 which are secured in the end wall 24. When the gyro is locked in caged position tension is maintained upon the cord 2| 2, the lever 202 being shifted counterclockwise from the position in which it is shown in Fig. l2 to `a position in which it engages the stop stud .2!5, in which position its end portion will overlie the end of the leaf spring |94. When it is desired to uncage the gyro, tension upon the cord 2|2 is released, whereupon the spring 208, acting through the bell crank lever 210, will swing the lever 202 clockwise to the position in which it is shown in Fig. l2, thus permitting the leaf spring |94 t0 flex outwardly and disengage the pin |96 from the socket 200 in the motor housing 42, thereby permitting the gyro casing to move relative to its support in response to changes in heading of the vehicle upon which the apparatus is mounted. A washer 2|8 may be secured to the stud `294 to limit the extent of outward flexing movement of the leaf spring The gyro mechanism may be utilized for any suitable purpose but is illustrated as forming part of an automatic steering mechanism more fully disclosed in my zo-pending application Serial No. 463,642, iiled October 28, 1942, now Patent No. 2,408,929. For this purpose a follow-up pulley 220 is mounted for free rotation upon the bearing bushing i60. Switch brackets 22.2 and 223 are secured to the pivot shaft |62. The bracket 1222 carries a flexible resilient switch arm 224 which is cooperable with a switch contact post secured to but insulated from the top frame 22, while the bracket 223 carries a iiexible resilient switch arm 225 suitably insulated therefrom. rThis switch arm 225 cooperates with a contact post 221 which is secured to the followup pulley 220 and grounded to the main frame through the follow-up pulley and its bearing. The switches 224, 22,6 and 225, 221 may be utilized to control an automatic steering apparatus, or any other mechanism which it is desired to operate in response to changes in the position of the frame relative to the gyro spin axis.

As shown in Fig. 14, the motor` |34 is series wound and is adapted to be energized upon closure of the main switch 230 which, through the brush arm |14 and slip ring |61, connects one terminal of the motor to a battery 23.2, the other terminals of the battery and the motor being grounded. Closure of the switch 230 also results in the connection of a conductor 234 to the ungrounded terminal of the battery 232.

A relay 236 has one terminal of its winding 230 connected to the conductor 234 and its other terminal connected t0 brush arm |16.so that the relay is energized whenevel the switch |02 is closed to connect the slip ring |86 to ground. The relay 236 includes a double-pole doublethrow reversing switch comprising switch arms 240, 24|. This switch operates to control the direction of rotation of motor |46, this motor operating in one direction when the relay 236 is energized and in the opposite direction when the relay is de-energized. Suitable anti-spark resistors 242, 243 and 244 are provided to inhibit arcing at the various contacts of the circuits. Such protection against arcing is particularly desirable when the apparatus is to be used in a rareed atmosphere.

In using the apparatus the main switch 230 is closed, thereby energizing the gyro motor |34. After the gyro motor has attained its normal operating speed, and the apparatus positioned in space so that the gyro spin axis points in a desired direction, the normally tensioned cord 2|2 is released to permit the spring 208 to swing the lever 26.2 clockwise (Fig. 12), and thereby remove its end portion 206 from obstructing position adjacent the leaf spring |94, whereupon the latei` will ex outwardly and withdraw the caging pin it from the socket 2639 in the gyro motor housing 4.12. Upon being thus released, the gyro casing will be free to swing about its horizontal pivot (to the extent limited by the stop pin |00) and will be relatively free to swing on its vertical pivot. For the purposes of this description, it will be assumed that the gyro spins counterclockwise as viewed in Fig. 3, and that at the instant or" uncaging of the gyro, the switch |02 happens to be closed.

rlhe relai7 236 will therefore be energized and the motor |45 will be rotating in a direction to drive the gear |40 clockwise (Fig. l0). rPhe gear |40, through the spring |42 and friction washer |38, exerts a clockwise torque upon the gimbal i4. The application of this torque causes the gyro to precess counterclockwise (Fig. 1) and such precession results in the opening of the switch |02, with consequent reversal of the direction of rotation of the motor |46 and application of a counterclockwise torque to the gim- Ibal 14. The application of counterclockwise torque to the gimbal 14 causes the gyro to precess clookwise (Fig. l) and the switch |02 closes to repeat the cycle.

Thus, when the frame of the apparatus is stationary, or continues to move in the same direction it was moving at the instant the gyro was uncaged, the gyro will precess through a Very small angle, first in one direction and then the other, at Very short intervals. The result will be that a torque will be applied to the vertical gimbal 14 iirst in one direction, and then in the other, in rapid alternation, with the ultimate eiect that the frictional torque and the torque due to the fiexure of switch arms 224, 225

--will be opposed by an equal and opposite torque will, in eiTect, be frictionless, and the torque appliedfthrough the gear |49 will be available for fthe operation of the switches 224-225 and 22E- 221, or for operating any other devices. -will be noted that the position of the stop portion |20 of the bracket ||2 determines the angular position of the gyro casing (relative to gimbal 14), atr which switch |02 opens as well as the position at which this switch closes, and that as a result, the angle through which precession f takes place is very minute.

The horizontal axis bearings are thus subjected to continuous agitation and the eiect of static friction is substantially eliminated, since rolling andL sliding friction are predominant.

If `the gyro casing is properly balanced it will continue to oscillate on its horizontal pivots through the minute angle, as above described, and the vertical gimbal 14 will accurately maintain its orientation in space. This fact is of considerable signicance in that it makes the balanc- `ing of the gyro casing about its horizontal axis a very simple operation.

lt is necessary merely to adjust the lweights '1B on the screws 68, .$59, until the gimbal 14 remains stationary. This balancing operation may thus be performed in a very short time. The frame may then be placed on end and adjustment of the weights on the screws 62, 63 quickly made in a similar manner. Such balancing also adjusts for the rotation of the earth for the particular latitude at which the adjustment is made.

It will now be assumed that the vehicle upon -which the apparatus is installed is acted upon by a force which causes it to turn the apparatus vclockwise `(Fig. 2).

to the change in direction of the vehicle is thus-l opposed by an equal (on the average) and opposite torque and, as a result, the gimbal will maintain its directional position in space.

While for purposes of description the action of 'the gyro was described as if substantial precession took place upon a change in orientation of the vehicle, such will seldom be the case. rlhis is because the gear Uit is driven at an angular velocity which is greater than any angular velocity of the vehicle which may normally occur. The erection of the gyro takes place continuously during the time that the vehicle is chang- `ing direction and the gyro will be in substantially erect position at all times. The only occasion upon which the gyro could precess through a? substantial angle would be if the vehicle changed direction violently at an angular velocity as great or greater than that at which the gear llil is driven. The apparatus is so designed that the angular velocity at which the gear M! may be driven is greater than any angular velocity which the vehicle may have. y

Ii the vehicle upon which the apparatus is mounted changes its direction so as to rhave a 4component about the horizontal axis-of 'the gyro `'casing,'-let us assumeinacounterclockwise direc- .tion (-Fligpl); the'effect will be the same as4 if the gyro had precessed'clockwise, so that-the erecting means-will operate in .thesame manner asy previously described, to cause the gyro spin axis to align itself with thenew directionfof movement of the vehicle in the vertical plane.

Thus, irrespective of the Ycharacter of the changes in direction of thefvehicle, the spin axis of the gyro will be maintained in al given horizontal orientation in space, although the spin axis will change with changes of direction of the Vehicle in the vertical plane. The position of the gyro axis, and hence that of the gimbal 84, thus provides an indication of the azimuthal component of the change in direction heading of the vehicle relative to the orientation of the vehicle at the time the gyro was uncaged.

The above described switch mechanism for controlling the operation of the procession correcting motor Ult, whereby the precession of the gyro ordinarily takes place through a very minute angle, is satisfactory and advantageous provided the horizontal bearings for the gyro casing pivots are formed with a very high degree of precision and have their :bearing surfaces very smoothly finished, or if the apparatus is used on a vehicle which is very frequently changing its heading, as for example, on a small boat traveling in a choppy sea. If, however, the horizontal pivot bearing r surfaces for the gyro casing are'not finished with extreme accuracy, or if a small particle of dirt, lint, or the like happens to get between the bearing surfaces, such irregularity in these bearings may introduce a factor tending to'decrease the accuracy of the apparatus.

In order to make it possible to manufacture the apparatus as economically as possible, without requiring high precision finishing of the horizontal bearings of the gyro casing, and to make the apparatus more reliable and accurate when used on a vehicle which maintains its heading steadily, as for example, a glider in flight through relative quiescent atmosphere, or a large ship traveling in a calm sea, I have provided the switch mechanism shown in Figs. l5 to 17 and the control circuit shown in-Fig. 18. Generally speaking, this mechanism permits oscillatory precession of the gyro through a greater angle thanthat permittedv by the previously described mechanism, and such oscillation has a longer period. But the ultimate effect is that of eliminating friction in the horizontal bearings.

In Figs. 15 to 18, such parts as correspond to previously described parts of the apparatus bear corresponding reference characters, and the detailed description thereof will not be repeated.

The switch mechanism is supported by a bracket 25u which is-secured to the arm lltlcarried by the gimbal lt. A pair of liexible resilient switch arms Zeil, 252 are secured to the bracket El by a screw .255, but are suitably in sulatecl therefrom, and from the bracket 250, by insulating washers 255. The switch arms 25E, are resiliently biased to engage a stepped insulating stop 258 which is riveted to the bracket 2F36. These flexible switch arms 25|, 2'52 have their contact ends in position to be engaged by the contact wire |86 on the pin |54 which Drojects from the stud 9G.

lt will be apparent, particularly from Fig. 16, that as the gyro casing precesses clockwise, the switch arm 525i will first be engaged by the contact pin lull, and as the gyro casing precesses further clockwise, the switch arm 252 will be engaged. Upon counterclockwise precessional movement of the gyro casing from the position in which both switches are closed, flexure of the switch arm .252 will first be arrested by the insulating stop 258 and contact with the pin |04 thus broken, while upon further counterclockwise precessional movement of the gyro, the ex ure of the switch arm 25| will be arrested and its contact with the contact pin |04 broken.

The effect of the operationof the switch arms 25|, 252 will best be understood by reference to Fig. 18, from which it will be noted that the switch arm 25| is connected through a third slip ring 260 and brush 262 to a switch arm 264 which forms part of a relay 266 and is closed when the winding .268 of the relay is energized. The switch arm 264 is adapted to complete a holding circuit for relay 265, this circuit including a conductor 210.

Let us assume that the main switch 230 has been closed and the apparatus is in operation, and a torque is applied to the gimbal 'lll through the friction washer |38 (or because of friction in the vertical gimbal bearings, or due to the operation of switches 224, 226 or 225, 221), in a direction such as to cause clockwise precession of the gyro casing from its position as indicated in Fig. 16 by the location of the contact pin |04. As the pin |84 makes electrical contact with the switch arm 25|, the relay 266 is not energized and the switch 254 is thus open, and the grounding of the switch arm 25| thus has no immediate eiect. As the gyro casing continues clockwise precession the switch arm 252 is engaged by the pin E24 and thus connected to ground. This completes an energizing circuit for the relay 255, which may be traced as follows: from battery 232, through switch 230, conductor 234, relay winding 268, brush |16, slip ring |65, switch arm 252, and contact pin ltd to the grounded terminal of battery 232.

The energizaticn of the relay 2GB results in reversal of the direction of rotation of the motor S56 through operation of the reversing switches 2413, 24|, and causes closure of switch 264 which, it will be noted, establishes a holding circuit for the relay. The holding circuit may be traced as follows: from battery 232, through switch 230, conductor 234, relay winding 268, conductor 2li), switch 264, brush 262, slip ring 260, switch arm 25|, and contact pin Ille to the grounded terminal of battery `232. The reversal of the direction of the motor Mt will, as previously described, result in the application of a torque to the gimbal 'i4 in a direction to cause counterclockwise precession of the gyro casing, whereupon the contact pin H34 will move away from switch arm 252, opening the initial relay energizing circuit. However, the relay will remain energized until upon further countercloclwise precession of the gyro casing, the contact pin itil moves away from the switch arm 25| as iiexure of the latter is arrested by the stepped stop 258. The latter results in opening the holding circuit for the relay 265, whereupon the relay is de-energized to permit return of the switches 24B, 24| to the position shown in Fig. 18, with the resultant reversal of the direction of rotation of the motor i4@ and consequent repetition of the above described cycle.

By virtue or" the spacing of the switch arms 25i, 252 the precessional oscillation of the gyro casing will take place through a small angle, in the order of 12, Such oscillation takes place continuously while the apparatus is in operation,

The period of such oscillation may be in the order of 10 to l5 seconds, depending upon the particular use to which the apparatus is to be put.

Since the angle through which the gyro casing may oscillate is accurately determined by the operation of the switches 25|, 252, the eect of a frictionless horizontal bearing for the gyro casing is obtained. This may be explained by the fact that the torque, due to actual bearing friction, is applied to the gyro casing for equal intervals of time in opposite directions, and since the torque due to friction is the same during the clockwise and counterclockwise precession of the gyro casing, the frictional torques cancel each other and thus over a period of time have no effect whatsoever upon the gyro casing. The energy necessary to overcome the friction in the horizontal bearings is supplied through the friction washer |38 from the motor |45. As previously pointed out, the motor |4i5, through the friction washer itil, also supplies the energy necessary to overcome friction in the vertical pivot bearings for the gimbal 'i4 as well as to overcome any torque on the gimbal resultant from the flexure of the switch arms 224, 225. Thus, though the vertical and horizontal pivot bearings are of rugged construction, the actual friction thereof cannot have any effect upon the directional characteristics of the gyro, and the result is the same as if these bearings were frictionless. The gyro axis can thus maintain its orientation with a very high degree of precision.

Because of this frictionless characteristic of the horizontal and vertical axis bearings, the gyro rotor need not be as large, nor need it spin as fast, as would otherwise be required, and the apparatus as a whole may be of relatively rugged and simple construction with consequent low cost of manufacture.

While I have shown and described particular embodiments of my invention, it will be apparent to those skilled in the art that numerous modifcations and variations may be made in the form and construction thereof, without departing from the more fundamental principles of the invention. I therefore desire, by the following claims, to include within the scope of my invention all such similar and modified iorrns of the apparatus disclosed, by which substantially the results of the invention may be obtained by substantially the same or equivalent means.

I claim:

l. ln a gyroscopic apparatus having, a, support, a vertical gmbal mounted for pivotal movement on a vertical axis in said support, a gyro case mounted for pivotal movement on a horizontal axis in said gimbal, and a gyro rotor and motor therefor mounted for rotation within said case on a normally horizontal axis perpendicular to the pivotal axis of the case; the combination of a gyro erecting reversible electric motor, a yielding driving connection between said erecting motor and said girnbal, a, relay having a winding, having switches for reversing the direction of rotation of said erecting motor, and having a holding switch, a pair of control switches closed sequentially as said gyro case rotates in one direction with respect to said gimbal and opened in reverse sequence as said gyro case rotates in the opposite direction, an energizing circuit for said relay including said winding and the last closed and first opened of said pair of switches, and a holding circuit for said relay including the other of said pair of switches and said holding switch.

2. In a gyroscopic apparatus, a gyro case, an

electric motor housing formingpart `or" said. case, a vrotary motor-armature having` a shaft, a gyro rotor secured tofsaidshaft, arpair of shaft .bearings in saidfmotor housing, one of said bearings being located` substantially at the center of gravity of the gyro case assembly, and means to yieldingly-,urge said shaft longitudinally against said last named bearing, whereby thelatter bearing fixes the longitudinal position of said shaft in said case.

3.v The-'combination set forth in claim 2 in Which said means comprises a compressed spring exerting its force between said motor housingl and ,said shaft.

4. In agyroscope, a shaft, a gyro-wheel secured to said shaft, a-frama a motor for driving said gyro wheel, said motorhaving a rotor part .secured tosaid shaft and having a-stator part secured to said frame,- a thrust bearingfor said shaft secured to said frame close to thecenter of gravtyof the assembly including said frame andall parts carried thereby, and yielding means urging said shaft longitudinally againstV said` thrust bearing, whereby the. centerof gravity of` said assembly will not be materially shifted uponV thermal expansionofthe-various parts of said assembly.

5. In-a gyroscope, arotary gyro wheel-assembly including a gyrowlieel, ashaft and a motor part,l

a gyrocasing-having a--thrust bearing -forsaid shaft, said thrust bearing being positioned -ina plane perpendicular to said shaft passingt'nrough the center of -gravityrof thewassembly-and being carried by said casing,andresilient means acting longitudinallyof said shaft to hold thelatter -in engagement with` said thrust bearing, whereby thermally produced changes in-the dimensions lof the rotating parts of said assembly-will notmaterially change the position of the-center of gravity of.. the -assembly.

6. In, aposi-tion determining 'control device-the combination of-Aamovable controlling element, a` pair ofv switchesA and Bllclosed'-successively-by said element -upon movement of #the-elementin one directionand opened.inl-areverse-order-upon movement of -the element-fin--the-reverse-direction, a, relay -havinga-winding andtwocontactors C and-D; a source ofelectrical energy;`v aholdingcircuit including `the source, switch A, contactor- C and the relay winding; a secondcircuit including the source, switchrB, and the Yrelay Winding; an electromagnetic Vmotor; anda third circuit including the source, contactor D,;and the electromagnetic motor.

7. In a gyroscopic apparatus having a supportingframe, a vertical gimbal mounted for ,pivotal movement on a vertical axis in said frame, a gyro case mounted for pivotalmovement in said gimybal .on a .horizontal axis,v and a gyro rotor and motor therefor mounted .for rotation within said case on a normally horizontal axis perpendicular to the pivotal axis of the case; the combination of ,a reversing gyroperecting motor, a frictionalv frdriving connectionv between said gyro erecting motor and said gimbal, a pair .of switches operated respectively vas said gyro vprecesses through"` predeterminedangles in opposite directions from.I

REFERENCES C'IED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,136,566V Usener Apr. 20, 1915 1,302,701 Parret May 6, 1919 1,687,970 Corliss Oct. 16, 1928 1,882,819 Hahnemann et al'. Oct. 18, 1932 1,887,318 Mahoney Nov. 8, 1932 1,959,052 Gilchrist May l5, 1934 2,050,542, Pace Aug. 1l, 1936 2,410,473 Weems Nov. 5, 1946 FOREIGN PATENTS` Number Country Date 108,776 Great Britain Aug. 23, 1917 

